Severe High-frequency Hearing Loss Research Articles

Patient Sex Mediates the Influence of Patient Age on Superior Canal Dehiscence Repair Outcome.

To investigate the independent and interactive effects of patient age and sex on superior canal dehiscence (SCD) repair outcomes. This was a cohort study of consecutive SCD repairs via the middle fossa approach at an institution between 2011 and 2022. We constructed multivariable regression models assessing surgical outcomes with age and sex as the primary predictors. Models controlled for surgery duration, follow-up duration, and relevant surgical and medical history. Subsequently, we repeated each model with the incorporation of an interaction term between patient age and sex. Among 402 repairs, average age was 50 years, and 63% of cases were females. There was a significant interaction between patient age and sex with respect to symptom resolution score (SRS) (adj. β 0.80, 95% C.I. 0.04-1.56). Older age was associated with lower SRS among females (-0.84, -1.29 to -0.39 point per year) but not significantly associated with SRS among males (0.04, -0.65 to 0.56 point per year). Furthermore, older age independently predicted a greater magnitude of increase in air conduction at 8000 Hz following surgery regardless of sex (adj. β 2.1, 0.2-4.0 dB per 10-year increase). This is the first study on the interactive effect between patient age and sex with respect to SCD repair outcomes. Older age predicted poorer symptomatic response among female patients but did not predict symptomatic response among male patients. Furthermore, older age predicted more severe high-frequency hearing loss following SCD repairs among both female and male patients. 3 Laryngoscope, 134:3363-3370, 2024.

Cochlear microphonic latency predicts outer hair cell function in animal models and clinical populations

As recently reported, electrocochleography recorded in cochlear implant recipients showed reduced amplitude and shorter latency in patients with more severe high-frequency hearing loss compared with those with some residual hearing. As the response is generated primarily by receptor currents in outer hair cells, these variations in amplitude and latency may indicate outer hair cell function after cochlear implantation. We propose that an absence of latency shift when the cochlear microphonic is measured on two adjacent electrodes indicates an absence or dysfunction of outer hair cells between these electrodes. We test this preclinically in noise deafened guinea pigs (2 h of a 124 dB HL, 16–24 kHz narrow-band noise), and clinically, in electrocochleographic recordings made in cochlear implant recipients immediately after implantation. We found that normal hearing guinea pigs showed a progressive increase in latency from basal to apical electrodes. In contrast, guinea pigs with significantly elevated high-frequency hearing thresholds showed no change in cochlear microphonic latency measured on basal electrodes (located approximately at the 16–24 kHz location in the cochlea).. In the clinical cohort, a significant negative correlation existed between cochlear microphonic latency shifts and hearing thresholds at 1-, 2-, & 4 kHz when tested on electrodes located at the relevant cochlear tonotopic place. This reduction in latency shift was such that patients with no measurable hearing also had no detectable latency shift (place assessed by CT scan, r’s of -.70 to -.83). These findings suggest that electrocochleography can be used as a diagnostic tool to detect cochlear regions with functioning hair cells, which may be important for defining cross-over point for electro-acoustic stimulation.

Audiological Management of Pediatric Oncology Patients

Audiological Management of Pediatric Oncology Patients

Benefits of Bimodal Hearing With Cochlear and Middle Ear Implants: Preliminary Results in Four Patients

Conventional hearing aids have some limitations in overcoming a large air-bone gap or in cases of severe high-frequency hearing loss. The authors aimed to evaluate the benefit of a new bimodal hearing configuration combining cochlear implantation (CI) and middle ear implant (MEI) in patients with severe mixed conductive and ski-slope hearing loss. Retrospective case review. Tertiary referral center. Four patients with severe to profound hearing loss, who underwent CI in one ear and MEI in the other, were enrolled. Audiological outcomes were assessed at least 6 months after the MEI/CI operation. Pure-tone audiometry (PTA) in unaided, CI-aided, and MEI-aided conditions were measured. Average threshold changes in bands of frequencies (<1 kHz, ≥1 kHz) were compared between MEI-aided and HA-aided conditions. The Korean version of the Hearing-in-Noise Test (K-HINT), and speech perception score in noisy and quiet conditions were evaluated in the bimodal configuration (i.e., MEI with CI). MEI-aided PTA was especially increased in high-frequency areas (≥1 kHz). Speech perception in noisy and quiet conditions demonstrated better scores in the bimodal configuration. K-HINT also demonstrated better scores in the bimodal configuration. There is an increasing number of patients with unilateral CI and residual hearing in the contralateral ear. The benefits of a new bimodal hearing configuration with CI and MEI were demonstrated in patients with severe high-frequency hearing loss or mixed conductive hearing loss in the contralateral ear.

Evaluation of a Frequency-Lowering Algorithm for Adults With High-Frequency Hearing Loss.

The objective was to determine the effects of a frequency-lowering algorithm (frequency composition, Fcomp) on consonant identification, word-final /s, z/ detection, the intelligibility of sentences in noise, and subjective benefit, for people with high-frequency hearing loss, including people with dead regions (DRs) in the cochlea. A single-blind randomized crossover design was used. Performance with Bernafon Acriva 9 hearing aids was compared with Fcomp off and Fcomp on. Participants wore the hearing aids in each condition in a counterbalanced order. Data were collected after at least 8 weeks of experience with a condition. Outcome measures were audibility, scores from the speech perception tests, and scores from a questionnaire comparing self-perceived hearing ability with Fcomp off and Fcomp on. Ten adults with mild to severe high-frequency hearing loss (seven with extensive DRs, one with patchy or restricted DRs, and two with no DR) were tested. Fcomp improved the audibility of high-frequency sounds for 6 out of 10 participants. There was no overall effect of Fcomp on consonant identification, but the pattern of consonant confusions varied across conditions and participants. For word-final /s, z/ detection, performance was significantly better with Fcomp on than with Fcomp off. Questionnaire scores showed no differences between conditions. In summary, Fcomp improved word-final /s, z/ detection. No benefit was found for the other measures.

Hearing Preservation Cochlear Implants: A Review of Potential Mechanisms of Hearing Loss After Implantation

Hearing preservation cochlear implants (CIs) are specifically designed to preserve residual low-frequency acoustic hearing for use together with electrically stimulated high-frequency hearing. This combined electro-acoustic stimulation (EAS) provides a promising treatment option for patients with severe high-frequency hearing loss, but with some residual low-frequency hearing, and has been shown to improve speech perception, especially in background noise, music perception, and sound source localization. Thus, preservation of residual hearing should be a priority in treatment.Although residual low-frequency hearing is successfully preserved to varying degrees in many patients, some patients experience a loss of residual hearing following implantation. A wide range of potential causes of, or contributors to, loss of residual hearing in EAS CI users have been proposed. In this paper, we review the evidence for several of the proposed causes of hearing loss with EAS CI. We conclude that its etiology is likely a multifactorial, heterogeneous phenomenon. Furthermore, we suggest that studies to further elucidate effects of ischemia on lateral wall function and maintenance of endocochlear potential in the context of EAS CI implantation and use are needed.

Hearing evaluation in patients with chronic renal failure

ObjectiveTo evaluate hearing threshold and the severity of hearing loss at different frequencies in patients with chronic renal failure (CRF), and to analyze the role of duration of disease on hearing threshold in patients of CRF by measuring pure-tone audiometry (PTA) and distortion-product otoacoustic emission (DPOAE). MethodsThere were analysed 61 subjects (122 ears) from which 12 were patients starting hemodialise (A), 24 subjects were patients undergoing hemodialise over a year (B), 15 subjects were patients undergoing conservative treatment (C) and 10 controls (D). We did hearing evaluation by testing them using tympanometry, PTA and DPOAEs. Other parameters (blood pressure, body weight, blood chemistries) were also evaluated. ResultsIt was found a severe high-frequency hearing loss among patients with CRF comparing to the control group. Duration on haemodialysis treatment does not seem to have a significant impact on the incidence of hearing loss, although the method of treatment may influence the impact of the disease on hearing. Hearing loss among patients with CRF seemed to deteriorate further a year after the first evaluation. ConclusionsDPOAE raised the percentages of detection of SNHL indicating that it is a better technique than the conventional PTA for evaluation of hearing acuity.

Predicting the perceived sound quality of frequency-compressed speech.

The performance of objective speech and audio quality measures for the prediction of the perceived quality of frequency-compressed speech in hearing aids is investigated in this paper. A number of existing quality measures have been applied to speech signals processed by a hearing aid, which compresses speech spectra along frequency in order to make information contained in higher frequencies audible for listeners with severe high-frequency hearing loss. Quality measures were compared with subjective ratings obtained from normal hearing and hearing impaired children and adults in an earlier study. High correlations were achieved with quality measures computed by quality models that are based on the auditory model of Dau et al., namely, the measure PSM, computed by the quality model PEMO-Q; the measure qc, computed by the quality model proposed by Hansen and Kollmeier; and the linear subcomponent of the HASQI. For the prediction of quality ratings by hearing impaired listeners, extensions of some models incorporating hearing loss were implemented and shown to achieve improved prediction accuracy. Results indicate that these objective quality measures can potentially serve as tools for assisting in initial setting of frequency compression parameters.

Traumatic ossicular disruption with isolated fracture of the stapes suprastructure: comparison with incudostapedial joint dislocation

Conclusion: More severe high frequency hearing loss, especially at 8 kHz, occurs with fracture of the stapes suprastructure (SSF) compared with isolated incudostapedial joint dislocation (ISD). Successful hearing gain can be achieved in the speech range with appropriate ossicular reconstruction. Objectives: Traumatic SSF is a rare consequence of head trauma. This study aimed to demonstrate the characteristic features of SSF compared with traumatic ISD. Methods: Eighteen patients who suffered from conductive hearing loss after head trauma and were operated from 2000 to 2012 were enrolled. Eight and 10 patients were confirmed to have a traumatic SSF (SSF group) and ISD (ISD group), respectively. The etiology of ossicular disruption, preoperative CT scan of the temporal bone, and intraoperative findings were retrospectively reviewed. Pre- and postoperative hearing was analyzed by both pure tone averages and thresholds at each frequency (0.5–8 kHz). Results: The most common etiologies in the SSF group were fall (n = 3) and direct ear trauma (n = 3), and for those in the ISD group, the most common etiology was traffic accident (n = 6). CT scan showed no evidence of fracture in the SSF group, whereas findings of ossicular dislocation were found in 70% of patients in the ISD group. Hearing outcomes according to the frequencies demonstrated that pre- and postoperative hearing loss at 8 kHz was more severe in the SSF group than in the ISD group. In a comparison of hearing outcomes at each frequency, the postoperative hearing threshold at 8 kHz was higher than for other frequencies. Postoperatively, 63% of the SSF group and 70% of the ISD group obtained an air–bone gap of within 15 dB.

Amplification for listeners with a moderately severe high-frequency hearing loss.

Some evidence exists to support the use of an extended bandwidth (EBW) for those with a relatively mild to moderate degree of hearing loss. The use of frequency lowering is suggested for those with a severe/profound degree of hearing loss. The amplification option for those with a moderately severe hearing loss in the high frequencies is less clear. This study compared three amplification options for listeners with a moderately severe hearing loss in the high frequencies. The efficacy of three amplification options-limited bandwidth to 4000 Hz, EBW, and frequency transposition-were evaluated for listeners with a moderately severe, high-frequency hearing loss. The experiment used a factorial repeated-measures design. A total of 13 adults with bilateral hearing loss of 50-70 dB HL at 4000 Hz served as test participants. The participants rated the sound quality of birdsongs and music when aided with the amplification options. Speech perception in quiet was measured at 50 dB SPL and 68 dB SPL input levels. The participants also completed a questionnaire on the best amplification option to use in different real-life environments during a 2 wk, take-home trial. The data were analyzed with repeated-measures analysis of variance. The findings showed that more listeners preferred the EBW for home use but that the frequency transposition was the least preferred. In addition, the performance of the EBW was better than that of the limited bandwidth in speech recognition but similar to that of the frequency transposition. The results supported the fitting of an EBW as the better choice for this group of listeners.

Efficient Hearing Screening in Noise-Exposed Listeners Using the Digit Triplet Test

Hearing screening in occupational medicine is generally based on pure-tone threshold audiometry. However, reliable and valid thresholds can only be obtained in a sound-proof room, using a high-quality, well-calibrated audiometer, and by a well-trained administrator. Thresholds also need to be determined for several audiometric frequencies. This makes the test time-consuming and expensive, which is not ideal for the screening of large populations. A Speech-In-Noise test (SPIN), by contrast, does not have the abovementioned requirements. Because it can be implemented as a quick automated self-test, possibly over the Internet, a SPIN test is highly advantageous for screening purposes. However, its sensitivity for (isolated) high-frequency hearing loss, as typically seen in noise-exposed listeners, was unclear up to present. In this study, the authors investigated the sensitivity and specificity of the Digit Triplet SPIN test for detecting and monitoring (early-stage) high-frequency hearing loss, and its similarity across two different language versions. One-hundred eighteen noise-exposed workers, representing a wide range from no to severe high-frequency hearing loss, completed the French or Dutch version of the broadband Digit Triplet self-test in an office-like room. Pure-tone thresholds, collected by a professional audiologist in favorable settings, served as the reference. The 84 Dutch-speaking participants showed a very strong linear relation between the reference and the Digit Triplet test, with the pure-tone average at 2, 3, 4, and 6 kHz as a strong predictor (R = 0.86) for the speech-reception threshold. The sensitivity and specificity to detect mild high-frequency hearing loss were 92% (61 of 66) and 89% (16 of 18), respectively. The area under the receiver operating characteristic (ROC) curve was very high (≥0.91) for several degrees of high-frequency hearing loss. With a within-subject standard deviation of only 0.8 dB, the Digit Triplet test also had a low measurement error. The results of the 34 French-speaking subjects showed a highly similar trend. The Digit Triplet test proves to have a high sensitivity and specificity for detecting different degrees of high-frequency hearing loss. Given its ease of use, this test is very suitable for screening purposes in occupational medicine, and potentially for the screening of adolescents at risk of recreational noise-induced hearing loss.

A Guinea Pig Model of Selective Severe High-Frequency Hearing Loss

Using an appropriate dose of an aminoglycoside antibiotic cotreated with a loop diuretic a guinea pig model of high-frequency loss can be obtained mimicking cochlear implant candidates with low-frequency residual hearing. We examined the stability of this model over time. A well-established method to create an animal model for profound deafness is cotreatment with an aminoglycoside antibiotic and a loop diuretic. Recent data indicated that reduction of the aminoglycoside dose might yield selective high-frequency hearing loss. Such a model is relevant for studies related to hybrid cochlear implant devices, for example, with respect to preservation of residual hearing. Guinea pigs received an electrode for chronic recording of compound action potentials to tones to assess thresholds. They were treated with a coadministration of kanamycin (200 mg/kg) and furosemide (100 mg/kg), after which, the animals were sacrificed for histologic analysis at 2, 4, or 7 weeks. After 2 to 7 weeks threshold shifts were greater than 50 dB for 8 to 16 kHz in 15 of 17 animals, whereas threshold shifts at 2 kHz or lower were less than 50 dB in 13 animals. Major threshold shifts occurred the first 2 to 4 days; subsequently, some spontaneous recovery occurred and, after 2-3 weeks thresholds, remained stable. Inner hair cell loss still progressed between 2 and 4 weeks in the most basal cochlear region; thereafter, hair cell loss was stable. An appropriate animal model for selective severe high-frequency hearing loss was obtained, which is stable at 4 weeks after ototoxic treatment.

Assessing the contribution of spectral cues to recognition of frequency-lowered consonants

Commercially available strategies for restoring audibility of critical high frequency cues to patients with severe high frequency hearing loss translate information from high-frequency regions with unaidable hearing to lower-frequency regions with aidable hearing. Methods for synthesizing lowered spectral features, rather than generating them from the signal, have been proposed, though no commercially available hearing aid uses such a method. We assessed consonant discrimination under three configurations of a spectral feature synthesis method intended for use in frequency lowering. Lowered consonants were rendered using one or two narrowband noise components presented in a low frequency region with aidable hearing. Different configurations conveyed different spectral cues intended to distinguish among lowered consonants. In a short pilot study, preliminary analysis found no significant difference in consonant matching accuracy between the different configurations, suggesting that listeners were not making use of additional spectral cues when they were available. However, there were some observable trends in the data, as well as open questions about the possible impact of training and acclimatization on listener performance. We will present the findings of a more extensive study to determine whether listeners with training can make use of enhanced spectral cues to distinguish among frequency-lowered consonants.

An Initial-Fit Comparison of Two Generic Hearing Aid Prescriptive Methods (NAL-NL2 and CAM2) to Individuals Having Mild to Moderately Severe High-Frequency Hearing Loss

Johnson and Dillon (2011) provided a model-based comparison of current generic hearing aid prescriptive methods for adults with hearing loss based on the attributes of speech intelligibility, loudness, and bandwidth. This study compared the National Acoustic Laboratories-Non-linear 2 (NAL-NL2) and Cambridge Method for Loudness Equalization 2-High-Frequency (CAM2) prescriptive methods using adult participants with less high-frequency hearing loss than Johnson and Dillon (2011). Of study interest was quantification of prescribed audibility, speech intelligibility, and loudness. The preferences of participants for either NAL-NL2 or CAM2 and preferred deviations from prescribed settings are also reported. Using a single-blind, counter-balanced, randomized design, preference judgments for the prescriptive methods with regard to sound quality of speech and music stimuli were obtained. Preferred gain adjustments from the prescription within the 4-10 kHz frequency range were also obtained from each participant. Speech intelligibility and loudness model calculations were completed on the prescribed and adjusted amplification. Fourteen male Veterans, whose average age was 65 yr and whose hearing sensitivity averaged normal to borderline normal through 1000 Hz sloping to a moderately severe sensorineural loss, served as participants. Following a brief listening time (~10 min), typical of an initial fitting visit, the participants made paired comparison of sound quality between the NAL-NL2 and CAM2 prescriptive settings. Participants were also asked to modify each prescription in the range of 4-10 kHz using an overall gain control and make subsequent comparisons of sound quality preference between prescriptive and adjusted settings. Participant preferences were examined with respect to quantitative analysis of loudness modeling, speech intelligibility modeling, and measured high-frequency bandwidth audibility. Consistent with the lack of difference in predicted speech intelligibility between the two prescriptions, sound quality preferences on the basis of clarity were split across participants while some participants did not have a discernable preference. Considering sound quality judgments of pleasantness, the majority of participants preferred the sound quality of the NAL-NL2 (8 of 14) prescription instead of the CAM2 prescription (2 of 14). Four of the 14 participants showed no preference on the basis of pleasantness for either prescription. Individual subject preferences were supported by loudness modeling that indicated NAL-NL2 was the softer of the two prescriptions and CAM2 was the louder. CAM2 did provide more audibility to the higher frequencies (5-8 kHz) than NAL-NL2. Participants turned the 4-10 kHz gain recommendation of CAM2 lower, on average, by a significant amount of 4 dB when making adjustments while no significant adjustment was made to the initial NAL-NL2 recommendation. NAL-NL2 prescribed gains were more often preferred at the initial fitting by the majority of participating veterans. For those patients with preference for a louder fitting than NAL-NL2, CAM2 is a good alternative. When the participant adjustment from the prescription between 4 and 10 kHz exceeded 4 dB from either NAL-NL2 (2 of 14) or CAM2 (11 of 14), the participants demonstrated a later preference for that adjustment 69% of the time. These findings are viewed as limited evidence that some individuals may have a preference for high-frequency gain that differs from the starting prescription.

Effects of electrical stimulation on the acoustically evoked auditory-nerve response in guinea pigs with a high-frequency hearing loss

Criteria for cochlear implantation keep expanding and people with substantial residual low-frequency hearing are considered candidates for implantation nowadays. Therefore, electro-acoustical stimulation in the same ear (EAS) is receiving increasing interest. We have investigated the effects of intracochlear electrical stimulation on acoustically evoked auditory-nerve activity, using a forward masking paradigm. The stimulation electrode was placed in the basal turn of the cochlea. Compound action potential (CAP) recordings were performed in guinea pigs with severe high-frequency hearing loss and in normal-hearing control animals. In normal-hearing animals, electrical stimulation generally suppressed CAPs, especially at high acoustic frequencies (8 and 16 kHz) and low sound levels. At low frequencies (0.5 and 1 kHz), suppression was observed only at high sound levels. In animals with a high-frequency hearing loss, suppression of CAPs at low frequencies was substantially less compared to control animals, even at high current levels and temporal overlap of acoustic and electric stimuli. Hence, effects of electrical stimulation substantially differed between normal-hearing animals and animals with a high-frequency hearing loss. These findings stress the need for a proper animal model when investigating EAS. We conclude that in case of high-frequency loss, the basal part of the cochlea can be stimulated electrically with little effect on responses to low-frequency acoustic stimuli.

Frequency-lowering devices for managing high-frequency hearing loss: a review.

Frequency-lowering technology has been around for decades. The primary aim--namely, that of providing high-frequency information to those with severe high-frequency hearing loss--addresses a clinical need most conventional hearing devices are still unable to provide. Early studies with frequency-lowering technology reported mostly unfavorable results, and the devices never gained clinical popularity. However, as hearing aid (HA) technology becomes ever more sophisticated, it is appropriate to reconsider whether frequency-lowering HAs should be an amplification choice in those with high-frequency hearing loss. Recent research is yielding promise with people who wear frequency-lowering devices showing improved speech perception. Questions remain regarding patient candidacy and whether auditory training may result in better outcomes. The author also discusses future clinical directions and research needs for frequency lowering.

Factors Affecting Outcomes on the TEN (SPL) Test in Adults with Hearing Loss

Recent work using the Threshold Equalizing Noise (TEN) test as a gold standard suggests that the presence of cochlear dead regions in persons with moderate-to-severe hearing loss may be quite common. In addition, previous data suggest that certain characteristics of hearing loss, such as severe-profound high-frequency hearing loss or steeply sloping configurations may be more commonly associated with positive TEN findings. These findings, however, are based largely on studies including a relatively small number of participants and/or participants that were included based on specific audiometric criteria (e.g., the presence of severe high-frequency hearing loss). Likewise, results from many of these studies are limited to the frequency regions of 500-4000 Hz. There has been less work that has systematically evaluated the relationship between audiometric characteristics and TEN test findings, particularly in the frequency regions above 4000 Hz, on a large number of individuals with a wide range of hearing losses and hearing loss configurations. The purpose of this study was to further examine the effects of audiometric characteristics such as degree and slope of hearing loss on the rate of positive, negative, and inconclusive findings on the TEN test over a wide frequency range (250-8000 Hz). Given that the functional impact of positive findings (i.e., findings suggestive of a dead region) may vary with the extent of potential damage, we were also interested in determining the relative occurrence of "patchy" versus contiguous positive findings on the TEN. Fifty-nine adults (117 ears) with a wide range of SNHL participated. To examine results over a wide frequency range (250-8000 Hz), the TEN (SPL), rather than the TEN (HL), was utilized. Thresholds, in both ears, were measured in quiet and in the TEN (SPL). Results were categorized as positive (suggestive of a dead region), negative (not suggestive of a dead region), or inconclusive. Consistent with past research, positive TEN (SPL) results were more common when hearing losses exceeded 60 dB HL; however, there was not a systematic increase in positive results with increases in threshold. In contrast to previous work, however, positive test results among individuals with milder hearing losses (< 60 dB HL) were not uncommon, suggesting a potential for false positive results. In regard to audiometric slope, also consistent with past research, slope of hearing loss was an inadequate predictor of TEN (SPL) results. Negative results (not suggestive of a dead region) were less common in participants with steeply sloping losses while positive test findings were unaffected by hearing loss slope. Although a large proportion of participants had positive results on the TEN (SPL), for most participants, these positive findings occurred in isolated (i.e., one or two frequencies) rather than in contiguous frequency regions. The relatively large number of inconclusive results and the potential for false positive results makes interpreting the functional impact of TEN (SPL) results difficult, particularly when positive results are in the high (> 4000 Hz) frequencies. In addition, although a large proportion (84%) of study participants had positive findings on the TEN (SPL), the functional impact of these findings is not clear as, in the majority of cases, positive findings occurred at only one or two test frequencies.

Integration of acoustic and electrical hearing

For some individuals with severe high-frequency hearing loss, hearing aids cannot provide a satisfactory improvement in speech recognition. However, these same patients often have too much residual hearing to qualify as candidates for a cochlear implant. Here we describe results with the Iowa/Nucleus Hybrid cochlear implant, which is designed to preserve the patient's residual low-frequency hearing while at the same time supplementing their high-frequency hearing through electrical stimulation. The advantages of this approach are presented, including improved speech recognition in competing backgrounds as compared with traditional cochlear implants. The results with the Iowa/Nucleus Hybrid device demonstrate the ability of the auditory system to integrate acoustic and electrical stimulation, even under conditions of severe distortions to the normal cochlear place-frequency mapping.

Combined acoustic and electric hearing: Preserving residual acoustic hearing

The topic of this review is the strategy of preserving residual acoustic hearing in the implanted ear to provide combined electrical stimulation and acoustic hearing as a rehabilitative strategy for sensorineural hearing loss. This chapter will concentrate on research done with the Iowa/Nucleus 10 mm Hybrid device, but we will also attempt to summarize strategies and results from other groups around the world who use slightly different approaches. A number of studies have shown that preserving residual acoustic hearing in the implanted ear is a realistic goal for many patients with severe high-frequency hearing loss. The addition of the electric stimulation to their existing acoustic hearing can provide increased speech recognition for these patients. In addition, the preserved acoustic hearing can offer considerable advantages, as compared to a traditional cochlear implant, for tasks such as speech recognition in backgrounds or appreciation of music and other situations where the poor frequency resolution of electric stimulation has been a disadvantage.

Dead regions in the cochlea at high frequencies: implications for the adaptation to hearing aids

SummaryIn patients with moderate to severe high-frequency hearing loss, cochlear damage may include “dead regions” where there are no functional inner hair cells and/or associated neurons. Aim: This study examines speech recognition in sensorineural impaired hearing patients with and without cochlear dead regions at high frequencies. Methods: a clinical and experimental study was made of thirty patients with sensorineural hearing loss that were classified into two groups: group 1 - included 15 subjects with hearing loss and no dead regions; and group 2 - included 15 subjects with dead regions in the cochlea at high frequencies. Patients undertook word recognition score and speech reception threshold tests, with and without background noise. The speech tests were done with and without hearing aids in two situations: program 1 - broadband amplification (bandwidth 8000 Hz); and program 2 - amplification up to 2560 Hz, without high frequency gain. Results: For subjects with no dead regions in the cochlea (group 1) performance improved with program 1. For subjects with dead regions in the cochlea (group 2) performance improved with program 2. Conclusions: Subjects with no dead regions in the cochlea benefited from high-frequency information. Subjects with dead regions in the cochlea benefited from reduced gain at high frequencies.